The invention relates to injection molding apparatus, and more particularly to co-injection apparatus, i.e., apparatus for injecting two different materials, typically an inner core material and an outer skin material, into a single multi-mold cavity.
A co-injection manifold receives material, usually plastic, from two different injection units and combines the two materials into a single stream that flows into a mold or die. The co-injection manifold is thus located between the injection units and the mold. A typical co-injection manifold is fixed to the injection units.
U.S. Pat. No. 4,376,625 discloses a co-injection manifold mounted on an injection unit, Another injection unit communicates with the co-injection manifold via a tube. The manifold has a forwardly opening outlet, an annular port axially behind or upstream of the outlet, and a central port axially behind or upstream of the annular port, One injection unit communicates with the central port, and the other injection unit communicates with the annular port. A valve member is movable between a fully forward position blocking both of the ports, an intermediate position blocking only the central port, and a rearward position clear of both ports. In the fully forward position, no material flows through the outlet. In the intermediate position, only material from the annular port flows through the outlet. In the rearward position, both material from the annular port and material from the central port flow through the outlet.